The present invention relates to vehicle seats provided with backs that can be folded down.
More particularly, the invention relates to a vehicle seat comprising a back and a seat proper, the back having at least a top portion mounted on a supporting strength member to pivot about a transverse horizontal pivot axis, said supporting strength member being connected to the seat proper (this supporting strength member can, in particular, constitute a portion of the seat proper, or it can form a bottom portion of the back, and it can be pivotally mounted to the seat proper by means of a hinge mechanism adapted to adjust the inclination of the back as a whole in order to improve comfort for the seat passenger), said top portion of the back being connected to the supporting strength member by a locking mechanism adapted to connect the top portion of the back to the supporting strength member at least in a raised, normal-use position, the locking mechanism being actuated by a control member accessible to a user to release the top portion of the back to pivot about said pivot axis, at least in order to enable it to pivot forwards from the raised position to a folded-down position.
Document FR-A-2 770 811 describes an example of such a vehicle seat, in which the locking mechanism comprises a hook mounted to pivot on the top portion of the back and engaging in a cutout secured to the strength member of the support. Although the device described in that document gives full satisfaction in terms of operation, that type of locking mechanism is expensive, in particular insofar as the hook and the piece in which the hook engages are usually made by a fine cutting-out process that is relatively expensive.
A particular object of the present invention is to mitigate that drawback.
To this end, according to the invention, in a seat of the kind in question, the locking mechanism comprises a locking cam pivotally mounted on a first seat element selected from the supporting strength member and the top portion of the back, the locking cam being urged resiliently towards a locking position and being movable towards a retracted position by actuating said control member, which member is carried by said first seat element, the locking cam having a bearing edge and a guide edge, and said locking cam being positioned and shaped so that:
when the top portion of the back is in the raised position and the locking cam is in the locking position, the bearing edge of said locking cam is wedged against a rigid peg fixed to a second seat element selected from the supporting strength member and the top portion of the back, said second seat element being different from the first seat element, the locking cam then preventing the top portion of the back from being folded down forwards and said top portion of the back then co-operating with the supporting strength member by coming into abutment therewith to prevent said top portion of the seat back from pivoting rearwards;
when the locking cam is in the retracted position, it does not interfere with said peg and it enables the top portion of the seat back to pivot from its raised position to its folded-down position; and
when the top portion of the back is in the folded-down position, said back can be raised freely, the locking cam then being disposed so that it does not lock against the peg, said locking cam being disposed so that its guide edge is in sliding contact against the peg at least during a portion of the raising stroke of the top portion of the back, the locking cam and the peg being disposed so that the peg slides along the guide edge of the locking cam towards the bearing edge when the top portion of the back pivots towards its raised position, the bearing edge of the locking cam being adapted to wedge against the peg when the top portion of the back returns to its raised position.
By means of these dispositions, the locking mechanism of the top portion of the back can be made in a low-cost manner since:
firstly the peg is a separate part that can be made at low cost; and
secondly the cam co-operates with the peg by a wedging effect, thereby accommodating any small lack of precision in manufacturing the cam or in assembling the cam or peg: this makes it possible to obtain locking that is very strong and snug for the top portion of the back while nevertheless using a standard manufacturing process for making the cam and assembling the seat, thus further reducing the cost price of the seat.
In addition, the cam is made easier to control by the fact that the cam and the control member are both carried by the same portion of the seat.
In preferred embodiments of the invention, use may optionally be made of one or more of the following dispositions:
the locking cam extends in a longitudinal direction between a first end pivotally mounted on the first element of the seat and a second end which includes the bearing edge of the locking cam, the guide edge of the locking cam extending between said first end and the bearing edge, the cam thus being braced against the peg of the second element of the seat while said locking cam is in the locking position, and the top portion of the back is in the raised position;
the bearing edge of the cam is shaped in such a manner that said locking cam cannot itself pass into the retracted position without a user actuating the control member when the bearing edge of the locking cam is wedged against the peg of the second element of the seat;
the locking cam is a piece of sheet metal having first and second main faces, the first main face of the locking cam being in sliding contact against a first side plate belonging to the first element of the seat and extending parallel to the locking cam;
the second element of the seat comprises a second rigid side plate which is parallel to the first side plate and which is secured to said peg, the locking cam being located at least in part between the first and second side plates, at least when the locking cam is in the locking position and the top portion of the back is in the raised position;
the second side plate is spaced apart from the second main face of the locking cam by a distance which is less than 3 millimeters (mm);
the second element of the seat includes a third side plate which is parallel to the first and second side plates, the second and third side plates being fixed to each other and defining between them a gap in which the first side plate and the locking cam are received, at least when the locking cam is in the locking position and the top portion of the back is in the raised position;
the second and third side plates are fixed to each other, firstly via the peg and secondly via at least one link wall which interconnects the second and third side plates and which co-operates with the first side plate by coming into abutment therewith to prevent rearward pivoting of the top portion of the back when said top portion of the back is in the raised position;
the first element of the seat is constituted by the top portion of the back and the second element of the seat is constituted by the supporting strength member; and
the first element of the sea: is constituted by the supporting strength member and the second element of the seat is constituted by the top portion of the back.